Direct reading micrometer gage and attachment therefor



Nov. 1, 1960 A. F. ANDERSON 2,958,136

DIRECT READING MICROMETER GAGE AND ATTACHMENT THEREFOR Filed Feb. 4,1958 FIG.1

ATTORNEYS United StatesPatent O DIRECT READING MICROMETER GAGE ANDATTACHMENT THEREFOR Alfred F. Anderson, 919 Forbes St, East Hal-word,Conn.

Filed Feb. 4, 1958, Ser. No. 713,145

Qlairns. (Cl. 33166) This invention relates to micrometer gages and,more particularly, to a micrometer gage of the direct reading type.

An object of the invention is to provide an improved direct readingmicrometer gage which is simple in design, economical of manufacture andreliable and accurate in use.

A further object of the invention is to provide apparatus in the form ofan attachment which may be connected to an existing micrometer gagewhich apparatus is adapted to provide direct readings of measurement ofsaid gage.

A more specific object of the invention is to provide apparatus of thetype described in the last above paragraph which may be pre-assembled asa self-contained unit and readily connected to an existing micrometergage of conventional construction.

The drawing shows a preferred embodiment of the invention and suchembodiment will be described, but it will be understood that variouschanges may be made from the construction disclosed, and that thedrawing and description are not to be construed as defining or limitingthe scope of the invention, the claims forming a part of thisspecification being relied upon for that purpose.

Of the drawing:

Fig. l is a side view of a micrometer gage embodying the invention;

Fig. 2 is an enlarged perspective view, partially in section, of aportion of the micrometer gage illustrated in Fig. 1;

Fig. 3 is a sectional view of a portion of the construction illustratedin Fig. 1, taken substantially along the line 3-3 thereof, the markedtape being removed for clarity of illustration; and r a Fig. 4 is a sideelevational view of a spiral spring illustrated in section in Fig. 3.

Referring particularly to Fig. 1 of the drawing, it will be seen thatthe micrometer gage there illustrated includes a frame which, inaccordance with conventional practice, is generally U-shaped. At one endof the frame, an anvil 12 is provided and the opposite end thereofconstitutes a support and a bearing guide 14 for a longitudinallymovable spindle 16. The support 14 has attached thereto a barrel 18which is threaded internally and through which extends the spindle 16which is provided over a portion of its length with mating externalthreads.

A sprocket wheel 20 is provided which is concentric with the spindle 16and is connected for rotation therewith. Said wheel 20 is located withina housing 30 which may be widely varied, one form of housing being shownin the drawing and being hereafter described in detail. Two take-uppulleys 24, 24 are located within the housing 30 and they are rotatableabout a common axis which is spaced from the axis of the spindle and isin fixed relation to said housing. Said pulleys 24, 24 are rotatableindependently of each other and each of them is free to make more thanone rotation. A flat perforated tape 22 extends over said sprocket wheel20 and is engaged 2,958,136 Patented Nov. 1, 1960 therewith so as to becarried thereover by rotation thereof with said spindle. The tape 22 ispreferably a flexible thin flat metal band which is resistant tostretching and said tape is provided with markings indicating units ofmeasurement of the micrometer gage. Said tape extends from said sprocketwheels to said take-up pulleys and it has its end portions coiledrespectively on said pulleys in opposite directions. A single spring 26is bodily rotatable about the axis of the pulleys and has its endsconnected respectively with said pulleys so as to tend to rotate them inwinding directions. Upon rotation of either pulley by one portion ofsaid tape in the unwinding direction said spring 26 serves to rotate theother pulley in the same direction to elfect winding of the otherportion of said tape thereon. Said spring 26 further serves duringwinding to rotate said other pulley at speeds varying from those of thefirst said pulley to compensate for varying diiferences in the unwindingand winding radii of the coiled portions of said tape on said pulleys.For registering with the markings provided on the tape 22, there isprovided a stationary indicator which is positioned adjacent the tape 22so that the markings thereon register successively with said indicatoron rotation of the spindle and pulley whereby to provide direct readingsof the micrometer gage.

While the invention in some of its aspects is not so limited, thedrawing shows the sprocket wheel 20 as being connected to a conventionalthimble 28 which surrounds a portion of the barrel 18 in the usualmanner and which extends longitudinally rearwardly therefrom beingcarried by a rearward portion of the spindle 16 and fixedly connectedthereto for rotation and for longitudinal movement therewith. When thethimble 28 is turned, the spindle 16 is rotated therewith and, by reasonof the threaded connection of said spindle with the barrel 18, saidspindle and thimble are moved longitudinally with respect to said barreland the forward end of the spindle 16 is thereby positioned in suitablyspaced relation with the anvil 12 for measuring a selected workpiece.The sprocket wheel 20 is thus connected with the spindle'16 indirectlyrather than directly and, when connection is made in such manner, thesaid housing 30 is movable relatively to the frame 10 and it has anopening 32 for receiving a portion of the thimble 28. As before stated,said housing also carries the first and second take-up pulleys 24, 24and encloses the tape 22.

Also provided is means engageable with the thimble 28 and adapted tohold the housing 30 in fixed relationship with the axis of said thimblewhile permitting free relative rotation of said thimble with respect tosaid housing and said means may comprise a sleeve 34 adapted forconnection to the thimble 28 for rotation therewith and further adaptedto be rotatably disposed in the opening 32 in the housing 30 with thesprocket wheel 20 connected thereto for rotation therewith. In addition,housing securing means is provided for preventing rotation of thehousing 30 about the axis of the thimble 28 and said means is preferablyadapted for connection with the frame 10 of the micrometer gage. Thus,in the preferred embodiment of the invention shown in the drawing, itwill be seen that the apparatus is provided in the form of an attachmentadapted for ready connection 'to an existing micrometer gage whichapparatus may be assernbled as a self-contained unit prior to attachmentto a with reference to the attachment of direct reading apparatus to anexisting micrometer gage previously provided withsuch scales. A scale 36is provided on the barrel 18 of the micrometer gage and said scaleincludes graduations-which are numbered from one to ten and thesegraduations are sub-divided into four spaces, each of which denotestwenty-five one-thousandths (.025) of an inch. The thimble 28 has agraduated scale 38 extending therearound at its forward end and dividedinto twenty-five spaces, eachfrepresen'ting one twenty-fifth of thedistance around said thimble. The scale 36 has an index mark 40 and aturn of the thimble 28 from zero to the first graduation mark thereonrepresents one onethousandth (.001) of an inch; that is, the end of thespindle 16 will be moved with respect to the anvil 12 the distance ofone one-thousandth (.001) of an inch and a full turn of the thimblerepresents twenty-five onethousandths (.025) of an inch, moving thethimble 28 along the scale 36 a distance of one graduation thereof anddenoting movement of the end of the spindle with respect to the anvil adistance of twenty-five one-thousandths (.025) of an inch.

The housing 36 preferably comprises two parts separated in a planenormal to the axis of the thimble 28 and said parts are adapted forinterengagement. Each part of the housing 30 is preferably provided withtwo openings, said openings being suitably sized and arranged therein soas to cooperate, when the two parts of said housing are interengaged asshown, to provide the aforementioned first opening 32 in said housingadapted to receive a portion of the thimble 28 and to provide a secondand smaller opening 42 spaced from Said first opening. The aforesaidsleeve 34 which is connectible with the thimble 28 of the micrometergage and adapted to be rotatably disposed in the housing opening 32preferably comprises a collet. Accordingly, each end portion of thesleeve 34 is threaded externally and is pro vided with a plurality oflongitudinally extending slots 44, 44. A suitable nut 46 is provided forengagement with each end of the sleeve or collet 34 and said nuts serve,when threaded securely on the ends of said collet, to force said colletinto friction-tight engagement with the thimble 28 whereby to providefor rotation and for longitudinal movement of the collet 34 and the nuts46, 46 with said thimble. When the collet 34 is disposed in the opening32 of the housing 30 and is engaged, as described, with the thimble 28of the micrometer gage, the two parts of said housing depend from thecollet and are held in interengagement and prevented from rotating withsaid collet by suitable means as described hereinbelow.

The means for preventing rotation of the housing 30 with the collet 34about the axis of the thimble 28 comprises, in preferred form, a rod 48which is connectible at one end thereof to the frame of the micrometergage. A clamp member 50 is connected to the rod 48 at one end thereofand is adapted for engagement with the frame 10, as by forcing the sidesof said member outwardly and sliding same over said frame. The other endof the rod 48 extends longitudinally from the clamp member 50 and isconnected to the housing 36). Preferably, the rod 48 extends into thesecond opening 42 which may be provided in said housing and the portionof said rod extending into said housing may be surrounded by a bushing52 disposed in said housing opening, the rod 48 being slidably engagedwith said bushing.

The bushing 52, in preferred form, is adapted to hold the two parts ofthe housing 30 in interengagement as well as to slidably receive aportion of the rod 48 and 1s provided at its ends with radiallyextending flanges, one of said flanges 54 being integral and the otherof said flanges55 being a nut engaging with threads formed on the end ofsaid bushing 52. When the bushing 52 is disposed in the second housingopening 42 and the nut is engaged with the end of said bushi g, t e t oParts f housing 30 are thereby held in interengagement as shown in thedrawing and, in addition, with the rod 48 extending into said bushingand connected at the other end thereof to the frame 10 of the micrometergage, the housing 30 is prevented from rotating with the collet 34 butis, however, free to move longitudinally.

The aforesaid main pulley or sprocket wheel 20 is preferably adapted forfixed connection with the collet 34 so as to be connected thereby to thethimble 28 for rotation and for longitudinal movement therewith and saidsprocket wheel may be formed integrally with said collet, as shown, oralternatively, the wheel 29 may be connected to the collet 34 by shrinkfitting or said wheel may be keyed or welded on Said collet. The tape 22which extends over the sprocket wheel 26 and which is provided withsuitable perforations for engaging the sprockets thereof so as to becarried oversaid wheel by rotation thereof is provided with markings asindicated above and when said tape is to be used with the micrometergage shown and described above, said markings preferably comprisenumbers each denoting one-thousandth of an inch. The numbers read, forexample with a one-inch micrometer gage adapted to measure in units ofthousandths of an inch, from 0 to 999 and said numbers are equallyspaced on the tape 22, the space thereoetween being such that the tapewill be carried over the sprocket wheel 20 a distance equal to saidspace by one twenty-fifth of a revolution of the thimble 28 denotinglongitudinal movement of the spindle 16 a distance of one-thousandth ofan inch. A complete revolution of the thimble 28 will result in movementof the tape 22 over the sprocket wheel 26 a distance of twenty-five ofsaid numbers. It will be understood that while the tape 22 is shown inthe drawing and described as being provided with a numbered scale graduated in thousandths of an inch, said scale may be graduated in otherdecimal parts of an inch or in other units of measurement or decimalpar-ts thereof as required for providing direct readings of measurementof micrometer gages of various types.

The take-up pulleys 24, 24 which are disposed in the housing 30 andadapted to receive and dischargethe tape 22 as it is discharged from andsupplied to the sprocket wheel 20 are preferably disposed adjacently andin coaxial relation with each other on a supporting rod 56 which may bemounted at each end thereof in the housing 30. The take-up pulleys 24,24 are freely rotatable on the supporting rod 56 and are rotatableindependently of each other and independently of the sprocket wheel 20except as controlled by the tape 22, the end portions of the tape beingcoiled respectively on said pulleys in opposite directions. Each of thepulleys is free to make more than one rotation so as to enable the tapeto be coiled thereon to any necessary extent.

The aforesaid spring means 26 is bodily rotatable about the axis of thepulleys and it urges the pulleys 24, 2 4 in suitable rotationaldirections for maintaining the tape 22 in tension. Said spring 26 ispreferably a flat spiral spring, as best illustrated in Fig. 4. Toaccommodate the spring 26, a coaxial cylindrical cavity 58 having oneend open is preferably formed in each of the pulleys 24, 24, saidcavities being in facing relation and in communication. The spring 26 ispreferably disposed within said cavities and attached at one end thereofto one of the take-up pulleys 24 and at the other end thereof to theother of said take-up pulleys as by the pins 60, 60, said spring beingin a slightlyflexed condition so as to urge said pulleys in oppositerotational directions. To secure the pulleys 24, 24 in the desired axialposition, a bushing 62 may be provided thereb'etween and a hub 64 formedon each of said pulleys for engaging mating shoulders 66, 66 formed onthe housing 30.

In order that the points atwhich the take-up pulleys 24, 24 dischargethe tape. 22 to the sprocket wheel 20 and receive said tape therefrommaybealigned with said sprocket wheel o i0 allow for proper engagementof the perforations in said tape with the sprockets of said wheel, ithas been found desirable to arrange the axis of the pulleys 24, 24angularly with respect to the axis of said sprocket wheel. Accordingly,the supporting rod 56 for the pulleys 24, 24 is mounted in the housing30 in a plane substantially normal to the plane separating the two partsof said housing, and said rod is angularly arranged with respect to theaxis of the thimble 28, as best illustrated in Fig. 3, so that the tape22 is twisted as it passes between the sprocket Wheel 20 and the take-uppulleys 24, 24, the longitudinal centerline of said tape therebetweenremaining, however, substantially within a plane normal to the axis ofsaid sprocket wheel.

The aforesaid stationary indicator provided for registering with themarkings on the tape 22 comprises, in the preferred embodiment of theinvention, a sight opening 68 provided in the housing 30 and positionedso that the markings on the tape 22 may be readily viewed therethrough.The sight opening 68 may have associated therewith an index mark 70 forfacilitating precise readings of the numbers on the tape 22.

Preferably, the housing 30 is provided with means adapted for movingsaid housing and the take-up pulleys 24, 24 carried therebylongitudinally with the collet 34 and sprocket wheel 20 as said colletand sprocket wheel are moved longitudinally with the thimble 28 onrotation of the latter. Said means preferably comprises aninternalrecess 72 formed in the housing 30 and adapted to receive a portion ofthe sprocket wheel 20, the sprocket wheel 20 being freely rotatablewithin said recess and the sides of said wheel engaging the sides ofsaid recess as required to cause the aforesaid longitudinal movement ofsaid housing.

The manner of assembling the apparatus described above and of connectingsame to a micrometer gage, as well as the operation thereof should beapparent from the foregoing and, therefore, only a brief description ofthe manner in which attachment of the assembled apparatus to amicrometer gage may be accomplished and of operation of the apparatuswith said gage is presented hereinbelow. When the apparatus has beenassembled as a unit, it may be attached to a micrometer gage byinserting the thimble 28 of the micrometer gage in the collet 34disposed in the opening 32 in the housing 30 and, by relative endwisemovement of said collet and thimble, the apparatus may be located in thedesired longitudinal position on said thimble. The collet 34 may then berotated as required with respect to the thimble 28 and the housing 30.to synchronize the numbers on the tape 22 with the spindle 16 of themicrometer gage whereupon the nuts 46 may be tightened and the clampmember 50 engaged with the frame of the gage.

With the apparatus operatively connected to the micrometer gage asdescribed and with a workpiece to be measured disposed between thespindle and the anvil, the thimble of said gage may be rotated in thenormal manner to advance the spindle toward the workpiece. Upon rotationof the thimble 28, the sprocket wheel 20 will be rotated therewith andwill carry the numbered tape 22 thereover, said tape being uncoiled fromone of the takeup pulleys 24, 24 and coiled up on the other of saidtakeup pulleys and the numbers on said tape appearing successivelythrough the sight opening 68 in the housing 30. When the spindle hasbeen advanced into contact with the workpiece and the proper tighteningtorque applied as with a conventional micrometer gage, the numberappearing through the sight opening 68 may be read by the operatorwhereupon he will be directly advised of the number of thousandths of aninch constituting the measured dimension of the workpiece.

The invention claimed is:

1. A direct reading micrometer gage comprising a generally U-shapedframe, a barrel fixedly connected with the frame, a rotatable spindleextending through the barrel and having threaded connection therewith, ahousing fixed against rotation with said spindle, a sprocket wheelconcentric with the spindle and connected for rotation there-,j withwhich wheel is located within said housing, two take-up pulleys locatedwithin the housing and rotatable about a common axis which is spacedfrom the axis of the spindle and is in fixed relation to saidhousingysaidpulleys being rotatable independently of each other and eachof them being free to make more than one rotation, a flat perforatedtape extending over said sprocket wheel and engaged therewith so as tobe carried thereover by rotation thereof with said spindle which tape isprovided with a series of markings for indicating units of measure mentof said gage, said tape having its end portions coiled respectively onsaid pulleys in opposite directions," a single spring bodily rotatableabout the axis of the pulleys and having its ends connected respectivelywith said pulleys and tending to rotate them in opposite wind ingdirections, said spring upon rotation of either pulley by one portion ofsaid tape in the unwinding direction serving to rotate the other pulleyin the same direction to effect winding of the other portion of saidtape thereon and further serving to rotate said other pulley at speedsvarying from those of the first said pulley to compensate for varyingdifferences in the unwinding and winding radii of the coiled portions ofsaid tape on said pulleys, and a stationary indicator on the housingadjacent the tape so that the markings on the tape register successivelytherewith to provide direct readings of said micrometer gage.

2. A direct reading micrometer as set forth in claim 1, wherein the axisof rotation of said take-up pulleys is at an angle to a plane throughthe spindle axis so' that'the center lines of the tape between saidsprocket wheel and said pulleys are approximately in a planeperpendicular to the spindle axis and extending through the center ofsaid sprocket wheel.

3. For use with a micrometer gage including a frame and a fixed barreland a rotatable spindle partly within the barrel and having threadedconnection therewith and a rotatable thim'ble carried by the spindle andsurrounding a portion of the barrel, an attachment comprising incombination, a housing separate from said frame and thimble and havingfirst and second openings therein, a sleeve disposed in said firsthousing opening for free rotation therewithin which sleeve is fixedlyconnectible with said thimble for rotation and for longitudinal movementtherewith, a sprocket wheel disposed within said housing and connectedto said sleeve for rotation and for longitudinal movement therewith,means on said housing engaging one of said longitudinally movable partsfor moving said housing longitudinally therewith, a rod fixedlyconnectible at one end thereof to said frame and extending into saidsecond housing opening for preventing rotation of said housing about theaxis of said thimble while permitting longitudinal movement thereof, twotake-up pulleys located within the housing and rotatable about a commonaxis which is spaced from the axis of the spindle and is in fixedrelation to said housing, said pulleys being rotatable independently ofeach other and each of them being free to make more than one rotation, aflat perforated tape extending over said sprocket wheel and engagedtherewith so as to be carried thereover by rotation thereof with saidspindle which tape is provided with a series of markings for indicatingunits of measurement of said gage, said tape having its end portionscoiled respectively on said pulleys in opposite directions, a singlespring bodily rotatable about the axis of the pulleys and having itsends connected respectively with said pulleys and tending to rotate themin opposite winding directions, said spring upon rotation of eitherpulley by one portion of said tape in the unwinding direction serving torotate the other pulley in the same direction to effect winding of theother portion of said tape thereon and further serving to rotate saidother pulley at speeds varying from those of the first said pulley tocompensate for varying differences in the unwinding and winding 7 radiiof the coiled portions of said tape on said pulleys, and a, stationaryindicator on the housing adjacent the tape so that the markings on thetape register successively therewith to provide direct readings of saidmicrometer gage.

4. An attachment as set forth in claim 3, wherein the axis of rotationof said take-up pulleys is at an angle to a plane through the spindleaxis so that the center lines of the tape between said sprocket wheeland said pulleys are approximately in a plane perpendicular to thespindle axis and extending through the center of said sprocket wheel.

5. For use with a micrometer gage including a frame and a fixed barreland a rotatable spindle partly within the barrel and having a threadedconnection therewith and a rotatable thimble carried by the spindle andsurrounding a portion of the barrel, an attachment comprising incombination, a housing separate from said frame and thimble and havingtwo parts separated in a plane normal to the axis of said thimble andsaid housing parts each having first and second openings therein, asleeve disposed in said first openings in the housing parts for freerotation therewithin which sleeve is fixedly connectible with saidthimble for rotation and for longitudinal movement therewith, a sprocketWheel disposed within said housing and connected with said sleeve forrotation and for longitudinal movement therewith, means, on said housingparts engaging one of said longitudinally movable parts for moving saidhousing longitudinally therewith, a rod fixedly connectible at one endthereof to saidframe and extending into said second housingopenings inthe housing parts, for preventing rotation, of said housing about theaxis of said thimble while permitting longitudinal movement thereof, abushing disposed in said second openings and surrounding a portion ofsaid rod, said bushing comprising two parts adapted to be fixedlyconnected together to hold said two housing parts in interengagement, aperforated tape extending over said sprocket wheel and engaged therewithso as to be carried thereover by rotation thereof which tape is providedwith a seriesof markings for indicating units of measurement of saidgage, two take-up pulleys disposed within said housing and engaging saidtape to receive and discharge portions thereof as said portions aredischarged from and supplied to said sprocket wheel, and a stationaryindicator positioned on the housing so that .the.markings on the tapesuccessively register therewith to provide direct readings ofsaidmicrometer gage.

References Cited in the file of this patent UNITED STATES PATENTS518,383 Wieland Apr. 17, 1894 1,361,156 Jaques Dec. 7,1920 1,370,310Gustavson Mar. 1, 1921 1,589,462 De Ghetto June 22, 1926 1,795,778Jaques Mar. 10, 1931 FOREIGN PATENTS 22,663 Great Britain 1904

